From: Stanislav Kinsburskii Date: Wed, 7 Jan 2026 18:45:43 +0000 (+0000) Subject: mshv: Align huge page stride with guest mapping X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=259add0d982cbe83170f0c2a9f160834f0f83dd4;p=thirdparty%2Fkernel%2Flinux.git mshv: Align huge page stride with guest mapping Ensure that a stride larger than 1 (huge page) is only used when page points to a head of a huge page and both the guest frame number (gfn) and the operation size (page_count) are aligned to the huge page size (PTRS_PER_PMD). This matches the hypervisor requirement that map/unmap operations for huge pages must be guest-aligned and cover a full huge page. Add mshv_chunk_stride() to encapsulate this alignment and page-order validation, and plumb a huge_page flag into the region chunk handlers. This prevents issuing large-page map/unmap/share operations that the hypervisor would reject due to misaligned guest mappings. Fixes: abceb4297bf8 ("mshv: Fix huge page handling in memory region traversal") Signed-off-by: Stanislav Kinsburskii Reviewed-by: Nuno Das Neves Reviewed-by: Michael Kelley Signed-off-by: Wei Liu --- diff --git a/drivers/hv/mshv_regions.c b/drivers/hv/mshv_regions.c index 30bacba6aec3..adba3564d9f1 100644 --- a/drivers/hv/mshv_regions.c +++ b/drivers/hv/mshv_regions.c @@ -19,6 +19,41 @@ #define MSHV_MAP_FAULT_IN_PAGES PTRS_PER_PMD +/** + * mshv_chunk_stride - Compute stride for mapping guest memory + * @page : The page to check for huge page backing + * @gfn : Guest frame number for the mapping + * @page_count: Total number of pages in the mapping + * + * Determines the appropriate stride (in pages) for mapping guest memory. + * Uses huge page stride if the backing page is huge and the guest mapping + * is properly aligned; otherwise falls back to single page stride. + * + * Return: Stride in pages, or -EINVAL if page order is unsupported. + */ +static int mshv_chunk_stride(struct page *page, + u64 gfn, u64 page_count) +{ + unsigned int page_order; + + /* + * Use single page stride by default. For huge page stride, the + * page must be compound and point to the head of the compound + * page, and both gfn and page_count must be huge-page aligned. + */ + if (!PageCompound(page) || !PageHead(page) || + !IS_ALIGNED(gfn, PTRS_PER_PMD) || + !IS_ALIGNED(page_count, PTRS_PER_PMD)) + return 1; + + page_order = folio_order(page_folio(page)); + /* The hypervisor only supports 2M huge page */ + if (page_order != PMD_ORDER) + return -EINVAL; + + return 1 << page_order; +} + /** * mshv_region_process_chunk - Processes a contiguous chunk of memory pages * in a region. @@ -45,25 +80,23 @@ static long mshv_region_process_chunk(struct mshv_mem_region *region, int (*handler)(struct mshv_mem_region *region, u32 flags, u64 page_offset, - u64 page_count)) + u64 page_count, + bool huge_page)) { - u64 count, stride; - unsigned int page_order; + u64 gfn = region->start_gfn + page_offset; + u64 count; struct page *page; - int ret; + int stride, ret; page = region->pages[page_offset]; if (!page) return -EINVAL; - page_order = folio_order(page_folio(page)); - /* The hypervisor only supports 4K and 2M page sizes */ - if (page_order && page_order != PMD_ORDER) - return -EINVAL; + stride = mshv_chunk_stride(page, gfn, page_count); + if (stride < 0) + return stride; - stride = 1 << page_order; - - /* Start at stride since the first page is validated */ + /* Start at stride since the first stride is validated */ for (count = stride; count < page_count; count += stride) { page = region->pages[page_offset + count]; @@ -71,12 +104,13 @@ static long mshv_region_process_chunk(struct mshv_mem_region *region, if (!page) break; - /* Break if page size changes */ - if (page_order != folio_order(page_folio(page))) + /* Break if stride size changes */ + if (stride != mshv_chunk_stride(page, gfn + count, + page_count - count)) break; } - ret = handler(region, flags, page_offset, count); + ret = handler(region, flags, page_offset, count, stride > 1); if (ret) return ret; @@ -108,7 +142,8 @@ static int mshv_region_process_range(struct mshv_mem_region *region, int (*handler)(struct mshv_mem_region *region, u32 flags, u64 page_offset, - u64 page_count)) + u64 page_count, + bool huge_page)) { long ret; @@ -162,11 +197,10 @@ struct mshv_mem_region *mshv_region_create(u64 guest_pfn, u64 nr_pages, static int mshv_region_chunk_share(struct mshv_mem_region *region, u32 flags, - u64 page_offset, u64 page_count) + u64 page_offset, u64 page_count, + bool huge_page) { - struct page *page = region->pages[page_offset]; - - if (PageHuge(page) || PageTransCompound(page)) + if (huge_page) flags |= HV_MODIFY_SPA_PAGE_HOST_ACCESS_LARGE_PAGE; return hv_call_modify_spa_host_access(region->partition->pt_id, @@ -188,11 +222,10 @@ int mshv_region_share(struct mshv_mem_region *region) static int mshv_region_chunk_unshare(struct mshv_mem_region *region, u32 flags, - u64 page_offset, u64 page_count) + u64 page_offset, u64 page_count, + bool huge_page) { - struct page *page = region->pages[page_offset]; - - if (PageHuge(page) || PageTransCompound(page)) + if (huge_page) flags |= HV_MODIFY_SPA_PAGE_HOST_ACCESS_LARGE_PAGE; return hv_call_modify_spa_host_access(region->partition->pt_id, @@ -212,11 +245,10 @@ int mshv_region_unshare(struct mshv_mem_region *region) static int mshv_region_chunk_remap(struct mshv_mem_region *region, u32 flags, - u64 page_offset, u64 page_count) + u64 page_offset, u64 page_count, + bool huge_page) { - struct page *page = region->pages[page_offset]; - - if (PageHuge(page) || PageTransCompound(page)) + if (huge_page) flags |= HV_MAP_GPA_LARGE_PAGE; return hv_call_map_gpa_pages(region->partition->pt_id, @@ -295,11 +327,10 @@ release_pages: static int mshv_region_chunk_unmap(struct mshv_mem_region *region, u32 flags, - u64 page_offset, u64 page_count) + u64 page_offset, u64 page_count, + bool huge_page) { - struct page *page = region->pages[page_offset]; - - if (PageHuge(page) || PageTransCompound(page)) + if (huge_page) flags |= HV_UNMAP_GPA_LARGE_PAGE; return hv_call_unmap_gpa_pages(region->partition->pt_id,